Hematology parameters as potential indicators of feed efficiency in pigs

Authors: Lindholm-Perry, Amanda; Kuehn, Larry; Wells, James - Jim; Rempel, Lea; Chitko-Mckown, Carol; Keel, Brittney; Oliver, William

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2021
Publication Date: 10/1/2021
Citation: Lindholm-Perry, A.K., Kuehn, L.A., Wells, J., Rempel, L.A., Chitko-McKown, C.G., Keel, B.N., Oliver, W.T. 2021. Hematology parameters as potential indicators of feed efficiency in pigs. Translational Animal Science. 5(4). Article txab219. https://doi.org/10.1093/tas/txab219.
DOI: https://doi.org/10.1093/tas/txab219

Interpretive Summary: Because the cost of feed is the largest expense to producers of meat animals, the ability to identify and select for animals that are more feed efficient is critical for profitability. However, determining feed efficiency requires measuring individual animal feed intakes using specialized and costly equipment. An indirect measurement for feed efficiency that is inexpensive and easy to sample would be of benefit to producers. The purpose of this study on a large group of pigs was to determine whether standard hematology measurements on whole blood would be predictive of an animal’s feed intake, body weight gain and gain-to-feed ratio. Whole blood samples were taken at days zero and 42 from pigs (N=178) that were monitored for individual feed intakes and body weight gain during a 6-week study. Blood samples were analyzed on a hematology instrument for white and red blood cell parameters. At day 0, platelet and lymphocyte counts were associated with feed intake, suggesting that they may have predictive value for feed intake. The strongest associations were with changes that occurred between day 42 and day 0 for red blood cell parameters, like red blood cell count, hemoglobin concentration and hematocrit (packed red blood cell volume). These were associated with both body weight gain and feed intake. Change in hematocrit from day 42 to day 0 was also associated with gain:feed ratio, a measure of feed efficiency. These standard hematology parameters, especially hematocrit, may be useful proxies to predict and select for feed efficiency in swine, and some may be useful for predicting swine feed intake.

Technical Abstract: The identification of an inexpensive, indirect measure of feed efficiency in swine could be a useful tool to help identify animals with improved phenotypes to supplement expensive phenotypes including individual feed intakes. The purpose of this study was to determine whether hematology parameters in pigs at the beginning and end of a feed efficiency study, or changes in those values over the study, were associated with average daily gain (ADG), average daily feed intake (ADFI), or gain-to-feed (G:F). Whole blood samples were taken at days 0 and 42 from pigs (n = 178) that were monitored for individual feed intakes and body weight gain during a 6-week study. Blood samples were analyzed for blood cell parameters including white blood cell (WBC), neutrophil, lymphocyte, monocyte, eosinophil and basophil counts, red blood cell (RBC) counts, hemoglobin, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC), platelet count, and mean platelet volume (MPV). Feed efficiency parameters were predicted using an ANOVA model including fixed effects of farrowing group and pen (sex constant) and individual hematology parameters at day 0, day 42 or their change as covariates. At day 0, platelet count was positively associated with ADFI (P < 0.05) and negatively associated with G:F (P < 0.1), and lymphocyte count was positively associated with ADFI (P < 0.05). At day 42, neutrophil, RBC counts, hemoglobin and hematocrit were asso¬ciated with ADFI (P < 10-3). Over the course of the study, changes in RBC measurements including RBC, hemoglobin, MCV, MCH, and MCHC (P < 10-4) which may improve oxygen carrying capacity, were associated with ADG and ADFI. The change in hematocrit over the course of the study was the only parameter that was associated with all three measures of feed efficiency (P < 0.05). Changes in RBC parameters, especially hematocrit, may be useful measurements to supplement feed efficiency phenotypes in swine.